1. Field of the Invention
This invention relates to a novel adsorbent for heavy metals which is obtained by treating active carbon with water-soluble amine and carbon disulfide, a process for production of the novel adsorbent, and an adsorption process using the novel adsorbent.
2. Description of the Prior Art
In recent times pollution caused by heavy metals contained in industrial waste water has become a significant problem, and chelate ion exchange resins have been highly valued as being effective for the adsorption removal of heavy metals from waste water. In particular, chelate ion exchange resins having chelate functional groups such as iminodiacetic acid and thiourea, with a phenol-aldehyde resin or a styrene resin as a base, have been put to practical use.
Such ion exchange resins, however, are insufficiently satisfactory in their adsorption capacity life (particularly for mercury ions) and production costs, and further improvements have been desired.
Japanese Patent Publication No. 22554/1978 discloses an adsorbent for use in removal of very small amounts of heavy metals, particularly mercury in gases, which is produced by depositing semicarbazide or its derivatives on active carbon; Japanese Patent Publication No. 8474/1979 discloses an adsorbent which is produced by depositing a sulfur-containing amino compound, such as thiourea, thiosemicarbazide, or thioacetamide, and sulfur-containing amino acid together with a hydrohalogenic acid on active carbon; and in Japanese Patent Publication No. 38597/1979, heavy metal-capturing materials are described which are produced by depositing barium sulfate, iron sulfide, zinc sulfide, manganese sulfide and dithiocarbamic acid derivatives on active carbon.
These adsorbents, however, are disadvantageous in that when they are used for removal of heavy metals in aqueous solutions, thiosemicarbazides, dithiocarbamic acid derivatives, and metal salts are partially dissolved since they are relatively soluble in water and separate from the active carbon. Moreover, they cannot be used at all for removal of mercury in concentrated sulfuric acid, nor can they be used for removal of mercury in saturated brine used in the sodium industry in an ion exchange membrane process. Furthermore, when they are charged in to a column, for example, for the disposal of waste water resulting from the washing of smoke in refuse incineration stations, the contact surface between adsorbent and water, adsorption capacity, mechanical strength and so on must be taken into consideration.
Thus a continuing need exists for adsorbents which are economical and of practical value.